In most experiments and applications utilizing lasers, it is desried to know the output power as a function of space and time. This could best be accomplished by using an inline power meter which does not obstruct the beam, which does not remove from the beam an appreciable number of photons, which has adequate spatial resolution, and which reads out the power with a response time short enough to indicate fluctuations of interest. Such an ideal device does not currently exist because low energy beams do not produce large enough effects and high energy beams tend to be too destructive. However, several attempts have been made to accomplish positions of this desired result. For example see U.S. Pat. No. 4,167,666, Sept. 11, 1979 (by T. G. Miller, B. O. Rogers, and T. G. Roberts); U.S. Pat. No. 4,035,088, July 12, 1977 and Canadian Pat. No. 1,132,372 (by A. H. Jenkins and J. J. Wachs); U.S. Pat. No. 4,458,496 issued Oct. 22, 1985 (by T. G. Roberts and T. E. Honeycutt); and most recently the work of C. H. Pyles, W. F. Otto, T. E. Honeycutt and T. G. Roberts as disclosed in U.S. patent application Ser. No. 707,294 filed Mar. 1, 1985.
The work of Pyles, et al provided a simple nonobstructing power meter for high energy pulsed lasers. This meter is simple, easy to build, easy to use, and easy to maintain. This device may readily be used either near the laser device to measure the output of the laser or near the target to measure the energy reaching a sample or target. (Such a device has also recently been used with a low power (4 watts) CO.sub.2 laser.) The response time of this device is of the order of 100 sec or less, and operates at pulse rates up to several tens per second with no cooling or only moderate cooling such as that produced by a fan. However, the usefulness of this device is limited because it integrates the energy within each laser pulse over both time and space. Thus, one obtains no information about these distributions within a pulse.
It is an object of this disclosure to provide a nonobstructing device which may be used to obtain information on the spatial distribution of the energy in a laser beam. It is a further objective of this disclosure to provide a device that may be used to accurately determine the position of a laser beam.
In many experiments it is necessary to align the laser beam along some desired optical path. This requires one to be able to locate the center of the laser beam with precision. This is currently difficult to accomplish especially in the infrared part of the spectrum. Also, there are many laser applications where the ability to determine with precision the positions of a laser beam would be useful such as in control loops to maintain alignment. An example would be in the use of laser welders, say, on an automobile assembly line. In such an application the device disclosed here could be used to monitor the position, alignment, and power in the laser beam, and still permit the welding action to be accomplished.